Pound one of the metal stakes into the ground at one corner of the garden bed. Hook the measuring tape to the stake and walk backward 8 feet. Pound the second stake into the ground at this spot. Continue the process, measuring at right angles until you complete the box. These are your guides for the next two steps.
Prepare the ground by clearing any debris, rocks or branches. Level off the ground with the claw rake as best as possible. Use the stakes as a guide to clear out the ground in between.
Dump the gravel into the middle of the square. Spread the gravel to a 3-inch thickness with the claw rake, using a back and forth motion. Once this is complete, remove the stakes. This is your drainage for the garden bed.
Place the first beam along one side of the cleared area. Place the second beam so that the end butts against the inside end of the first beam. Line up the corner. Place the third beam so the end butts against the inside end of the second beam and line up the corner. Place the fourth beam into position the same way. This is the base of the garden bed.
Place the first beam of the second row so the end of the beam overlaps the end of the beam below it. Then repeat the step above until all four sides are complete. Do the same steps for the third tier as well.
Fill in the garden bed with clean fill and no rocks. This helps the root system. Fill up the soil to the first tier of the bed and spread out with the claw rake. Tamp it down with the shovel. Continue filling each tier the same way until you reach the top of the bed. Once the last layer of soil is spread, don't tamp it down. Keep the last layer loose to plant seeds and seedlings.